In this paper, overall heat transfer coefficient and friction factor of water based γ-Al2O3 nanofluid in a double tube counter flow heat exchanger have been measured experimentally under turbulent flow condition. For better dispersion of γ-Al2O3 nanoparticles in distilled water, magnetic stirrer and ultrasonic vibrator (with a power of 240 kW and frequency of 35 kHz) were implemented. The stabi...

In this paper, Wavelet Collocation Method has been used to solve nonlinear fin problem with temperature dependent thermal conductivity and heat transfer coefficient. Thermal conductivity of fin materials varies any type so that we consider thermal conductivity as the general function of temperature.  Here we consider three particular cases, where we assume that thermal conductivity is constant,...

in this paper, turbulent mixed convective heat transfer of water and al2o3 nanofluid has been numerically studied in a horizontal tube under non-uniform heat flux on the upper wall and insulation in the lower wall using mixture model. for the discretization of governing equations, the second-order upstream difference scheme and finite volume method were used. the coupling of pressure and veloci...

ADiesel cycle enginewith internal and external irreversibilities of finite combustion rate of the fuel, friction and heat leakage is investigated in this paper. The heat transfer between the working fluid and the environment outside the cylinder obeys generalized radiative heat transfer law [q ∝ ∆(T n)]. Under the conditions of the fixed total cycle time and fuel consumed per cycle, the optimal...

BACKGROUND AND OBJECTIVES Cryogen spray cooling (CSC) is used to pre-cool the epidermis during dermatological laser procedures such as treatment of port wine stain (PWS) birthmarks, hair removal, and non-ablative photorejuvenation. Thus far, heat transfer studies related to CSC optimization have assumed a flat surface but clinical observation suggests that human skin indents due to the force of...

in this paper, overall heat transfer coefficient and friction factor of water based γ-al2o3 nanofluid in a double tube counter flow heat exchanger have been measured experimentally under turbulent flow condition. for better dispersion of γ-al2o3 nanoparticles in distilled water, magnetic stirrer and ultrasonic vibrator (with a power of 240 kw and frequency of 35 khz) were implemented. the stabi...

in this paper the numerical analysis of flow and time dependent heat transfer of micro-tube conveying nanofluid in laminar flow is investigated. in this study, convection heat transfer of nanofluid and base fluid and transient analysis for time-varying heat flux for time step of 0.0001 second are elucidated. it is observed that the pumping power of nanofluid flowing and the maximum temperature ...

the effect of γ-al2o3 nanoparticles on heat transfer rate, baffle spacing and pressure drop in the shell side of small shell and tube heat exchangers was investigated numerically under turbulent regime. γ-al2o3-water nanofluids and pure water were used in the shell side and the tube side of heat exchangers, respectively. since the properties of γ-al2o3-water nanofluids were variable, they were ...

This paper provides a review on the fouling mechanism and its effect onto the performance of finned tube heat exchangers in HVAC systems. Fouling tends to degrade the performance of heat exchangers by decreasing the heat transfer coefficient and increasing the air-side pressure drop across the heat exchangers. Air side fouling depends on a number of factors on the air side, including type and c...

An experimental study of heat transfer characteristics with and without insert was found using water –water system on 1-2 pass shell and tube heat exchanger. Experimental results such as exchanger effectiveness, overall heat transfer coefficient were calculated using with and without insert. There is improvement in overall heat coefficient, efficiency in using twisted tape. In all the process i...